The goal of this proposed study is to further the understanding of the role of the central nervous system in the regulation of body temperature. Fever will be used as a tool to achieve this aim. By observing and quantifying the alterations in both behavioral and physiological thermoregulatory activity in response to fevers produced by preoptic anterior hypothalamic (PO/AH) injections of prostaglandin E1 (PGE1), we hope to obtain tangible results. a) An understanding of how the peripheral and central elements of the thermoregulatory system integrate to produce a regulated body temperature and how this process is altered to produce fever. b) A comparison of the effects of fever on thermoregulatory behavior and autonomic temperature regulating outputs. c) Information of how pryogens and other noxious stimuli act on the brain to raise the set point of the physiological and behavioral thermoregulator to cause a controlled elevation of body temperature - fever.